Abrading – Machine – Rotary tool
Reexamination Certificate
1999-06-08
2001-11-20
Hail, III, Joseph J. (Department: 3723)
Abrading
Machine
Rotary tool
C451S444000, C451S449000, C134S0570DL, C134S153000
Reexamination Certificate
active
06319105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing apparatus that includes a dressing device to maintain the surface quality of a polishing tool while minimizing polishing defects on a workpiece such as a semiconductor wafer.
2. Description of the Related Art
As the density of circuit integration in semiconductor devices becomes ever higher, circuit patterns are becoming finer and interline spacing narrower. In this type of technology, the depth of focus becomes very shallow in photolithographic reproduction of circuit patterns, and it requires that the surface of the wafer placed at the focal plane of a stepper must be microscopically flat to produce the required degree of image sharpness. As illustrated in
FIGS. 4 and 5
, a method of obtaining a flat surface is to polish the workpiece in a polishing apparatus comprised by a turntable
12
having a polishing tool
10
such as a polishing cloth or a grinding stone thereon, and a top ring (wafer holding member)
14
known as chemical mechanical polishing (CMP).
In the conventional CMP apparatus, a wafer W is held on the bottom surface of the top ring
14
, and the wafer is pressed against the polishing cloth
10
mounted on the rotating polishing table
12
by means of a pressing cylinder. During the polishing process, a polishing solution Q is supplied from a nozzle
16
so that polishing action takes place while the polishing solution Q is retained between the wafer surface to be polished and the polishing cloth
10
.
The ability of the polishing cloth
10
to provide efficient surface material removal becomes degraded as polishing is continued, and to regenerate the polishing ability of the polishing cloth
10
, a dressing device
18
is used at suitable intervals, such as when exchanging wafers. The dressing device
18
is disposed opposite to the top ring
14
across the center of the turntable
12
. The dressing device
18
, similar to the top ring
14
, may be attached to a swing arm
20
so that it can be swung back and forth between the dressing position above the polishing cloth
10
on the turntable
12
and a standby position outside of the turntable
12
. Dressing tool
24
is attached to a shaft
22
at the bottom end of the arm
20
, so that it can be driven by an elevating device and a rotation device. A dressing operation is carried out by rotating the turntable
12
and the dressing tool
24
and pressing the dressing tool
24
onto the work surface of the polishing cloth
10
.
After dressing is finished, the dressing tool
24
returns to the standby position, but because the tool
24
has been contaminated with polishing debris and polishing solution adhering to the polishing cloth
10
, it is necessary that the tool
24
be cleaned before the next cycle of dressing. For this purpose, a cleaning device
28
having a container
26
filled with a cleaning solution L is placed in the standby location, and the dressing surface of the dressing tool
24
is immersed in the cleaning solution L, as shown in
FIG. 6. A
similar device has also been used to clean the top ring.
However, in such a conventional cleaning device, even if a fresh solution L is used each time, there is always a chance of contamination of the fresh solution L by spent polishing solution or polishing debris that were removed from the dressing tool
24
during the previous cleaning step and are adhering to the inner surface of the container
26
. Also, polishing debris adhering to the bottom surface of the dressing tool
24
float into the cleaning solution L, and when the dressing tool
24
is immersed in the cleaning solution L, the solution level rises, the debris will adhere to upper surfaces
24
a
or side surfaces
24
b
of the tool
24
(see FIG.
1
). Furthermore, mist produced during the normal polishing operation of the polishing solution can sometimes adhere to the upper surfaces
24
a
or side surfaces
24
b
of the tool
24
, and such a contaminant cannot be removed simply by immersing the tool
24
in the cleaning solution L. such contaminants can sometimes fall on the polishing cloth
10
during the dressing operation. Such dried and solidified contaminants that have fallen on the polishing cloth
10
have been known to cause scratching on the polished surface of the wafer.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polishing apparatus to include a cleaning device for critical cleaning of the top ring or the dressing tool to obtain high quality polishing by minimizing surface damage caused by contaminants originating from the top ring and/or dressing tool.
This object is achieved in a polishing apparatus comprising: a polishing table; a workpiece holding member for pressing a workpiece onto the polishing table; a dressing tool for conditioning a work surface provided on the polishing table; and a cleaning device for cleaning the dressing tool and/or the workpiece holding member; wherein the cleaning device is provided with a spray nozzle for directing a cleaning solution toward at least an upper surface of the workpiece holding member or the dressing tool.
Accordingly, the present polishing apparatus enables cleaning the top ring or the dresser in a fresh cleaning solution free of residual contaminants originating from such areas as the solution container, and critically cleaning the upper surface of the workpiece holding device or the dressing tool, which has been difficult to do with conventional cleaning devices. Therefore, the workpiece holding member holding a wafer can now be made totally clean, and the dressing tool can be cleaned thoroughly so that dressing of the polishing cloth can be performed without the fear of contaminating the polishing cloth by particles detached from the dressing tool. The overall result is that superior polishing is achieved by the polishing apparatus of the present invention.
The cleaning device may be provided with a covering member to prevent splashing of cleaning solution. Accordingly, polishing scum and debris are prevented from flying out of the cleaning device so that high pressure sprays can be used to clean the dressing tool or the workpiece holding device.
The cleaning device may be provided with a solution storage section for immersing at least a lower surface of the workpiece holding device or the dressing tool. Accordingly, spray cleaning and immersion cleaning can be combined to provide an even more effective cleaning process.
The cleaning device should be made corrosion resistant in those regions of solution passages and/or solution contacting parts. Accordingly, reactive chemicals which might be needed for cleaning some polishing materials may be used.
The cleaning device may be provided with a control section for controlling operation of the spray nozzle. Accordingly, a most effective cleaning method can be chosen to suit each application.
Therefore, as explained above, the present cleaning device with the spray cleaning produces superior cleaning compared with using immersion cleaning only. Furthermore, an important advantage is the reliability of removing contamination from the upper surface of the workpiece holding device or the dressing tool, which has been a difficult task using the conventional cleaning devices. Therefore, probability of contamination by a dressing tool or a workpiece holding device is reduced significantly, to enable a high quality of polishing on workpieces required for advanced device production.
REFERENCES:
patent: 5486131 (1996-01-01), Cesna et al.
patent: 5664987 (1997-09-01), Rentleln
patent: 5836947 (1998-11-01), Kimura et al.
patent: 5944894 (1999-08-01), Kitano et al.
patent: 5975994 (1999-11-01), Sandhu et al.
patent: 6036582 (2000-03-01), Aizawa et al.
U.S. Patent Application Ser. No. 08/807,810, filed Feb. 26, 1997, by Tetsuji Togawa et al, entitled “Polishing Apparatus”, in Group Art Unit 3723, status pending.
Sakurai Takeshi
Takada Nobuyuki
Togawa Tetsuji
Ebara Corporation
Hail III Joseph J.
McDonald Shantese
Wenderoth , Lind & Ponack, L.L.P.
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